Various types of electrocautery devices for incising and cauterizing body tissue are known and used in the medical field. Typically, such devices include a conductive tip or needle which serves as one electrode in an electrical circuit which is completed via a grounding electrode coupled to the patient. Incision of tissue is accomplished by applying a source of electrical energy (most commonly, a radio-frequency generator) to the tip. Upon application of the tip to the tissue, a voltage gradient is created, thereby inducing current flow and related heat generation at the point of contact. With sufficiently high levels of electrical energy, the heat generated is sufficient to cut the tissue and, advantageously, to simultaneously cauterize severed blood vessels.
It is widely recognized in the prior art that the often substantial amount of smoke produced by electrocauterization of tissue is at least unpleasant, and in some cases distracting or even hazardous to the operator and other attending medical personnel. As a result, it has been proposed, and is common, to provide an electrocautery device with smoke-aspirating capabilities, such that the smoke produced from electrocauterization is quickly withdrawn from the area of incision. Smoke aspiration may be accomplished by providing, in the handle of the electrocautery device near the electrocautery tip/electrode, an inlet port to be coupled to a vacuum or suction source. Examples of this are described in U.S. Pat. No. 4,307,720 to Weber, Jr., entitled "Electrocautery Apparatus and Method and Means for Cleaning the Same;" in U.S. Pat. No. 5,242,442 to Hirschfeld, entitled "Smoke Aspirating Electrosurgical Device;" and in U.S. Pat. No. 5,269,781 to Hewell, entitled "Suction Assisted Electrocautery Unit."
It has also been recognized in the prior art that the accumulation of coagulated blood, tissue rubble, and other debris on the electrode/tip of an electrocautery device can present a problem for the operator, necessitating the periodic cleaning of the tip, e.g., by wiping the tip over sterilized gauze or the like. This is generally regarded as undesirable, since the need to clean the electrode/tip tends to interrupt the incision procedure and increases the risks associated with contamination of the tip or the incision, damage to the tip, injury to the operator, and the like. To address this problem, it has been proposed in the prior art to provide an electrocautery instrument in which the electrode/tip is in slidable engagement with the instrument's handle, such that when the tip is retracted into the hand, any adhering debris automatically scraped off onto the tip of the handle. Such an instrument is proposed in the above-referenced Weber, Jr. '720 patent. While this arrangement may have some benefit, it still may be necessary to wipe off the tip of the handle once the tip is retracted. It is believed that a more direct and effective approach to the problem would be to reduce the amount of debris created during the electrocautery process, thereby eliminating or at least reducing the need to clean the electrode/tip.
Atrial fibrillation is the condition where the normal rhythmic contractions of the heart are replaced by rapid irregular twitchings of the muscular heart wall. At least 1 million people in the U.S. suffer from atrial fibrillation. There are at least three detrimental side effects that occur during atrial fibrillation: a rapid irregular heartbeat; impaired cardiac hemodynamics due to a loss of AV synchrony; and an increased vulnerability to thromboembolism. Surgical Treatment of Cardiac Arrythmias by Willis Hurst pg. 867.
The typical treatment for atrial fibrillation has been to give the patient drugs. For most patients with atrial fibrillation, this therapy has been only moderately effective and has typically produced undesirable side effects.
In view of the problems with drug therapy to treat atrial fibrillation, it has been recognized as desirable to find a surgical treatment that would permanently cure atrial fibrillation. Cardiovascular Device Update,July 1995,pg. 1. Although radiofrequency catheter ablation (RFCA) has proven to be a safe and effective way of treating the most benign causes of supraventricular tachycardia (SVT), such as Wolff-Parkinson-White and AV nodal re-entry tachycardia, using ablation to treat atrial fibrillation has proven to be challenging. Id.
The so called "maze" procedure has been developed to treat atrial fibrillation. In the "maze" procedure, incisions are made into the right and left atria via an open chest surgical procedure. These incisions are located to interrupt all the potential re-entry circuit patterns that could occur in the atria and cause atrial fibrillation. The clinical success with the "maze" procedure has been good.
A problem with the "maze" procedure is that it requires open chest surgery which is undesirable. It has been recognized that it would be desirable to duplicate the "maze" procedure with ablation. Id. at pg. 3. This would allow the possibility of performing a "maze"-like procedure thorascopically. However, it has also been recognized that current ablation technology has not developed to allow the "maze" procedure to be duplicated with ablation. Id.
A problem with prior art ablation has been that the ablating tip, if left in contact with a piece of tissue for too long, will burn through and perforate the tissue. In many applications, it has proven difficult to balance leaving an ablating tip in position on a piece of tissue for a sufficient time to allow the tissue to be ablated but not leave it in place for a length of time to burn through and thereby perforate the tissue.
Another problem with prior art ablation devices is that if the ablating tips are left in contact with the tissue too long, the tip "sticks" to the tissue being ablated. In removing the tip, large portions of tissue are often removed attached to the tip. This is not only a result to be avoided because of the tissue damage, but it is time consuming and irritating to the physician. These are clearly problems to be avoided.